What is Indoril architecture outside of Mournhold? Do they have thier own personal architecture? Do they use Vivec-esque architecture? Do they use temple architecture? Do they use Mournhold architecture? Do they use the very dungeon looking Old-Mournhold architecture?
I don't think Mournhold could be a good example of the unquestionable definate Indoril architecture, it may be the Indoril captial, but it was built by and for Almalexia, on top of old ruins, which look completely different to Mournhold.
What armour do Indorils use? I think I read somewhere that the reason Ordinator armour is called Indoril armour, is because most ordinators are a part of Indoril. I may be wrong there. Perhaps being a part of House Indoril requires you to be a part of the Temple? Being so close to the Temple, and most Indoril member wear it.
Apparently, Accoring to TIL, in the first five lessions of Vivec, there's often talk of an "egg of Vivec" in a "netchiman's wife" that was ordered to take to House Indoril. How metaphorical could this be? It could be a nice twist to have Vivec's child. If so, what would happen with the whole heart of Lorkhan mess? Could it be possible to affect the child of one who uses it? We've never known anyone who done this to have a child, so I'm not too sure. And, if not, would Vivec protect this child with divine measures? Or would he want him to live a "normal" life, with risk and injury? Being a god can distort your perception of mortal desires.
How tolerant of the Empire are they? No Great House, other than Hlaalu are in favour of them, but some are tolerant. There's a few Telvanni and Redoran towns with Imperial influence. Remember that the majority of powerful Indoril nobles killed themselves after knowing they'd be serving the Empire.
Are there any known ranks? I'm not sure what to call the guy in charge of Indoril, as he's only reffered to as the High Counsiler, which is because he's a part of Morrowind's counsil.
What are relations with the other houses? They seem likely allies with House Dres seem to be another "orthodox" house, being reliant on slavery, and opposing the empire. I read on TIL, that "Houses Dres and Indoril would fight to the death", if the treaty where to be passed. I guess this means that they'd fight together against the Empire, since they have similar wants. I know they hate House Hlaalu.
Is there a reason why there's no Indoril influence in Vvardenfell? They seem one of the most likely to be there, being so close to the Temple.
It would also be nice to share anything I mightn't know. Be it speculation or lore. I'd like to implement as much as possible.
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I believe that's all for now. While I'm here, I'll share my plot. Some parts may be negated to the question above. Don't worry about it;
The whole point of the early questline of House Indoril involves you finding the son of Vivec. You'll be involved in a plot to remove Helseth from the throne and replace him with the son of Vivec. This will all be ordered to you by the second-in-command, in secret. Once you find out of the plot, you can tell the Hlaalu guy in charge, and settle for the place of the second-in-command, or continue to do everything. If you continue with the plot, you'll eventually become involved in another plot to kill the High Counciller. Once this happens, the second-in-command guy will be promoted to the new guy in charge of Indoril. You will then be told to help with the reccomendation of this guy to be in the council, and become the High Councilman himself. You'll have to journey around to some high-up members of Morrowind. You'll need to go to the likes of Vedam Dren, Orvas Dren, The High ranking members of other great houses apart from Hlaalu, and members of the Temple. You'll have to convince members of the great houses that he's a good choice for the interests of thier house.
Once the guy in charge is announced High Counsiler, He'll demote himself down, and place you incharge of the House. You'll be able to then chose a second-in-command, and use him to build up your stronghold. It will be the first Indoril stronghold in Vvardenfell. (The Indoril base for quests will be located in Mournhold)
You'll then be able to change the sway of things yourself. You can chose to settle the fighting with Hlaalu, by letting them become influential in your stronghold, or corrupt them, and they will eventually fall. You'll be able to take House Hlaalu, and earn thier profits.
You can also chose to kill Vedam Dren, and eventually remove Imperial influence from Vvardenfell, letting you control them, and earning profits from them, or you can side with them, and let them have influence in your stronghold.
Does all this make sense regarding to lore? I thought I'd give the ability to join with the Empire/Hlaalu, incase the player is corrupt, himself.